In industrial sewing machines, that is, sewing machines adapted especially for commerical fabrication of sewn articles of commerce as opposed to the class of sewing machines generally referred to as home sewing machines, the amount of sewing achieved per day is relatively high. Accordingly, operator fatigue is a much more significant factor than in home or domestic sewing machines. Moreover, the rate of production is of more economic significance such as to justify various power assisted operations of portions of the machine that would not be economically justified in a home or domestic machine. For example, many industrial sewing machines are provided with power assisted presser foot lifts and the power assist may be provided, for example, by means of an electrically operated solenoid or by means of a pneumatic cylinder. The power actuating means can be under the operators direct control, as by a treadle, knee or hand control or may be automatic in nature whereby a specific set of stitches is to be repetitively performed by the machine and the presser foot then automatically lifted at the end of the sewing cycle as in a cam controlled machine, an electronic pattern machine, or the like.
Even when the power actuator means for lifting the presser foot is present to relieve operator fatigue, it is sometimes desirable to provide a manual override thereof for manual actuation by the operator and under certain circumstances it is especially desirable that such a manual override provide fine control of the presser foot rise to less than the amount of lift that would be appropriate at the end of a seam or stitching operation. For example, it is sometimes desirable to feather the elevation of the presser foot for sewing over especially heavy felled or lapped seams or for providing sharp curvature seams.
There have been previously disclosed presser lifting arrangements with both manual and power driven actuators utilizing a single lost motion connection so that the operation of the manual actuator does not effect movement back into the power actuator mechanism. In such previously known arrangements, however, operation of the power actuator will effect movement of the manual actuating mechanism which could be fatiguing or annoying to the operator.